Magnetic Molecules are tomorrows bits synthetic?

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1 Magnetic Molecules are tomorrows bits synthetic? Jürgen Schnack Department of Physics - University of Osnabrück schnack/ 25. Juni 2002 unilogo-m-rot.jpg

2 ? Contents Contents VDI-Technology Prognosis Molecular Magnets What are magnetic molecules? Structure of magnetic molecules Example for magnetic makro molecules Magnetic molecules as storage media? Magnetic molecules as storage media? Light Induced Excited Spin State Trapping (LIESST) Further applications of magnetic molecules Research funding for magnetic molecules unilogo-m-rot.jpg Jürgen Schnack, Universität Osnabrück, Magnetic Molecules are tomorrows bits synthetic? 1

? VDI-Technology Prognosis Molecular Magnets VDI-Technology Prognosis Molecular Magnets 1987 first ferromagnetism in an metal-organic substance (T c < 4.

3 ? VDI-Technology Prognosis Molecular Magnets VDI-Technology Prognosis Molecular Magnets 1987 first ferromagnetism in an metal-organic substance (T c < 4.8 K); 1989 discovery of the LIESST effect (Light-Induced Excited Spin State Trapping) with spin crossover substances; 1990 first ferromagnetism in a pure organic substance (T c < 1 K, today T c < 35.5 K); 1991 ferromagnetism in an metal-organic substance (T c > 350 K); 1996 discovery of macroscopic magnetisation tunneling in a single crystal of metal-organic nanomagnets. unilogo-m-rot.jpg Jürgen Schnack, Universität Osnabrück, Magnetic Molecules are tomorrows bits synthetic? 2

4 ? What are magnetic molecules? What are magnetic molecules? macro molecules, e.g. polyoxometalates: consist of constituents like Hydrogen (H), Carbon (C) and Oxygen (O) as well as paramagnetic ions like Iron (Fe), Chromium (Cr), Copper (Cu), Nickel (Ni) or Manganese (Mn); pure organic magnetic molecules: magnetic coupling between high spin molecules (e.g. free radicals); intermolecular interaction relatively small. unilogo-m-rot.jpg Jürgen Schnack, Universität Osnabrück, Magnetic Molecules are tomorrows bits synthetic? 3

? Structure of magnetic molecules Structure of magnetic molecules dimers (Fe 2 ), tetrahedra (Cr 4 ), cubes (Cr 8 ); rings, especially iron rings (Fe 6, Fe 8, Fe 10,.

5 ? Structure of magnetic molecules Structure of magnetic molecules dimers (Fe 2 ), tetrahedra (Cr 4 ), cubes (Cr 8 ); rings, especially iron rings (Fe 6, Fe 8, Fe 10,... ); complex structures (Mn 12 ); soccer balls, more precisely icosidodecahedra (Fe 30 ) and other macro molecules. unilogo-m-rot.jpg Jürgen Schnack, Universität Osnabrück, Magnetic Molecules are tomorrows bits synthetic? 4

6 ? Example for magnetic makro molecules Example for magnetic makro molecules {Mo 72 Fe 30 } unilogo-m-rot.jpg Jürgen Schnack, Universität Osnabrück, Magnetic Molecules are tomorrows bits synthetic? 5

7 ? Magnetic molecules as storage media? Magnetic molecules as storage media? Advantages: every molecules is a domain of its own; very weak intermolecular interactions; high density and nevertheless good separation of magnetic moments; high spin possible, e.g. S = 10; magnetic molecules show hysteresis; theoretically possible storage density: 40 Tbits per square inch, today: 20 Gbits per square inch (IBM), 300GB per square inch (Fujitsu 05/2002) unilogo-m-rot.jpg Jürgen Schnack, Universität Osnabrück, Magnetic Molecules are tomorrows bits synthetic? 6

8 ? Magnetic molecules as storage media? Magnetic molecules as storage media? Disadvantages: magnetisation tunneling! stabilisation by appropriate substrate? (Prof. Blügel, Osnabrück/Jülich, often very small coupling (J 10 K), i.e. thermally unstable at room temperature; recording head must be very small and needs precise guide. mbdssrew/winpeny intro3.html unilogo-m-rot.jpg Jürgen Schnack, Universität Osnabrück, Magnetic Molecules are tomorrows bits synthetic? 7

? Light Induced Excited Spin State Trapping Light Induced Excited Spin State Trapping (LIESST) magnetic molecules may serve as optical switches or displays; materials: spin crossover substances which

9 ? Light Induced Excited Spin State Trapping Light Induced Excited Spin State Trapping (LIESST) magnetic molecules may serve as optical switches or displays; materials: spin crossover substances which show the LIESST effect; principle: reversible change in colour when irradiated with laser light or when heated as well as cooled. unilogo-m-rot.jpg Jürgen Schnack, Universität Osnabrück, Magnetic Molecules are tomorrows bits synthetic? 8

? Further applications of magnetic molecules Further applications of magnetic molecules magnetic molecules may act in biological systems, e.g. as transport media, collecting device or for precise drug deposition (patent Dr.

10 ? Further applications of magnetic molecules Further applications of magnetic molecules magnetic molecules may act in biological systems, e.g. as transport media, collecting device or for precise drug deposition (patent Dr. Peter Borrmann); magnetic molecules may be used as contrast material in resonance tomography; magnetic molecules may be useful as catalysts or in quantum computers. unilogo-m-rot.jpg Jürgen Schnack, Universität Osnabrück, Magnetic Molecules are tomorrows bits synthetic? 9

? Research funding for magnetic molecules Research funding for magnetic molecules EU: Thermal and Optical Switching of Molecular Spin States (TOSS); DFG: Key program 1137: Molecular

11 ? Research funding for magnetic molecules Research funding for magnetic molecules EU: Thermal and Optical Switching of Molecular Spin States (TOSS); DFG: Key program 1137: Molecular Magnetism; DOE: z.b. Ames-Lab, Iowa, USA; DAAD-NSF: mutual exchange program. unilogo-m-rot.jpg Jürgen Schnack, Universität Osnabrück, Magnetic Molecules are tomorrows bits synthetic? 10

12 ? Ende Thank you very much for your attention. Collaboration Prof. K. Bärwinkel, Prof. H.-J. Schmidt, Prof. S. Blügel, D. Mentrup, M. Exler,... (Uni Osnabrück); Prof. M. Luban, Prof. R. Modler, Dr. P. Kögerler (Ames Lab, Iowa, USA); Dr. Chr. Schröder (Telelogic, Bielefeld); Prof. J. Richter (Uni Magdeburg); Dr. A. Honecker (Uni Braunschweig). unilogo-m-rot.jpg Jürgen Schnack, Universität Osnabrück, Magnetic Molecules are tomorrows bits synthetic? 11

The end is (not) in sight: exact diagonalization, Lanczos, and DMRG

The end is (not) in sight: exact diagonalization, Lanczos, and DMRG Jürgen Schnack, Matthias Exler, Peter Hage, Frank Hesmer Department of Physics - University of Osnabrück http://www.physik.uni-osnabrueck.de/makrosysteme/